U.S. patent application number 10/612697 was filed with the patent office on 2005-01-06 for lithium cell with improved cathode.
Invention is credited to Bofinger, Todd, Chi, Ignacio, Cintra, George, Nanjundaswamy, Kirakodu.
Application Number | 20050003269 10/612697 |
Document ID | / |
Family ID | 33552567 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050003269 |
Kind Code |
A1 |
Nanjundaswamy, Kirakodu ; et
al. |
January 6, 2005 |
Lithium cell with improved cathode
Abstract
A primary lithium cell having an anode comprising lithium and a
cathode comprising electrochemically active material selected from
copper vanadates having the formula CuV.sub.2O.sub.6 or
Cu.sub.2V.sub.2O.sub.7 or mixtures thereof. The cathode can include
a manganese dioxide in admixture with said copper vanadates. The
cell exhibits higher capacity and energy output than conventional
lithium cells having an anode comprising lithium and cathode
comprising manganese dioxide.
Inventors: |
Nanjundaswamy, Kirakodu;
(Sharon, MA) ; Bofinger, Todd; (Nashua, NH)
; Chi, Ignacio; (Mahtomedia, MN) ; Cintra,
George; (Holliston, MA) |
Correspondence
Address: |
Barry D. Josephs
Attorney At Law
19 North St.
Salem
MA
01970
US
|
Family ID: |
33552567 |
Appl. No.: |
10/612697 |
Filed: |
July 2, 2003 |
Current U.S.
Class: |
429/220 ;
429/224; 429/231.1; 429/231.5; 429/232 |
Current CPC
Class: |
H01M 6/14 20130101; H01M
4/483 20130101; H01M 4/502 20130101 |
Class at
Publication: |
429/220 ;
429/231.5; 429/231.1; 429/224; 429/232 |
International
Class: |
H01M 004/48; H01M
004/62; H01M 004/50 |
Claims
What is claimed is:
1. An electrochemical cell comprising a housing, a positive and a
negative terminal, an anode comprising lithium, a cathode
comprising a cathode active material selected from the group of
vanadate compounds consisting of CuV.sub.2O.sub.6 and
Cu.sub.2V.sub.2O.sub.7 and any mixture thereof.
2. The cell of claim 1 wherein said cell is nonrechargeable.
3. The cell of claim 1 wherein said cathode active material
selected from the group of vanadate compounds consisting of
CuV.sub.2O.sub.6 and Cu2V2O7 and any mixtures thereof, comprises
between about 1 and 95 percent by weight of the cathode
(electrolyte free basis).
4. The cell of claim 1 wherein said cathode active material further
comprises a manganese dioxide.
5. The cell of claim 1 wherein said cathode further comprises
manganese dioxide heat treated to remove water therefrom.
6. The cell of claim 1 wherein said cathode further comprises a
lithiated manganese dioxide.
7. The cell of claim 1 wherein said cathode further comprises a
conductive carbon comprising graphite.
8. An electrochemical cell comprising a housing, a positive and a
negative terminal, an anode comprising lithium, a cathode
comprising CuV.sub.2O.sub.6, and a nonaqueous electrolyte.
9. The cell of claim 8 wherein the cell is nonrechargeable.
10. The cell of claim 8 wherein said cathode further comprises a
manganese dioxide.
11. The cell of claim 8 wherein said cathode further comprises a
lithiated manganese dioxide.
12. The cell of claim 8 wherein the CuV.sub.2O.sub.6 comprises
between about 1 and 95 percent by weight of the cathode
(electrolyte free basis).
13. The cell of claim 8 wherein the CuV.sub.2O.sub.6 comprises
between about 60 and 95 percent by weight of the cathode
(electrolyte free basis).
14. The cell of claim 8 wherein said cathode further comprises
manganese dioxide heat treated to remove water therefrom.
15. The cell of claim 8 wherein said cathode further comprises a
lithiated manganese dioxide.
16. The cell of claim 8 wherein said cathode further comprises a
conductive carbon comprising graphite.
17. An electrochemical cell comprising a housing, a positive and a
negative terminal, an anode comprising lithium, a cathode
comprising Cu.sub.2V.sub.2O.sub.7, and a nonaqueous
electrolyte.
18. The cell of claim 17 wherein said cell is nonrechargeable.
19. The cell of claim 17 wherein said cathode further comprises a
manganese dioxide.
20. The cell of claim 17 wherein the Cu.sub.2V.sub.2O.sub.7
comprises between about 1 and 95 percent by weight of the cathode
(electrolyte free basis).
21. The cell of claim 17 wherein the Cu.sub.2V.sub.2O.sub.7
comprises between about 60 and 95 percent by weight of the cathode
(electrolyte free basis).
22. The cell of claim 17 wherein said cathode further comprises
manganese dioxide heat treated to remove water therefrom.
23. The cell of claim 17 wherein said cathode further comprises a
lithiated manganese dioxide.
24. The cell of claim 17 wherein said cathode further comprises a
conductive carbon comprising graphite.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a lithium electrochemical cell
with a cathode comprising copper vanadates selected from
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7, and mixtures
thereof.
BACKGROUND OF THE INVENTION
[0002] Electrochemical cells commonly contain a negative electrode
(anode) and a positive electrode (cathode), an electrolyte
permeable separator therebetween and an electrolyte in contact with
both of the electrodes. Electrolytes can be aqueous-based or
non-aqueous organic solvent-based liquid electrolytes or polymeric
electrolytes. There are two basic types of electrochemical cells, a
primary (nonrechargeable) and a secondary (rechargeable) cell. A
primary electrochemical cell is discharged to exhaustion only once.
A secondary electrochemical cell, however, is rechargeable and thus
can be discharged and recharged multiple times.
[0003] Primary (non-rechargeable) lithium cells have an anode
comprising lithium and a cathode comprising manganese dioxide, and
electrolyte comprising a lithium salt such as lithium
trifluoromethane sulfonate (LiCF.sub.3SO.sub.3) dissolved in a
mixtures of nonaqueous solvents. These lithium cells (Li/MnO.sub.2
cells) are commonly in the form of button (coin shaped) cells,
prismatic or polyhedral cells (wherein one or more of the housing
surfaces are flat, typically of cuboid, namely, rectangular
parallelepiped shape) or cylindrical cells, e.g. 2/3 A cell having
about 2/3 the height of conventional AA alkaline cells. (The 2/3 A
cell has an IEC designation "CR17335" and has a diameter of about
15 mm and height of about 32 mm). The Li/MnO.sub.2 cells have a
voltage of about 3.0 volts which is twice that of conventional
Zn/MnO.sub.2 alkaline cells and also have a higher energy density
(watt-hours per cubic centimeter of cell volume) than that of
alkaline cells. (Alkaline cells as referenced herein shall be
understood to be conventional commercial alkaline cells having an
anode comprising zinc, a cathode comprising manganese dioxide, and
an electrolyte comprising aqueous potassium hydroxide.) Therefore,
Li/MnO.sub.2 cells can be used in compact electronic equipment,
especially photographic cameras, which require operation at higher
voltage and at higher power demand than individual alkaline
cells.
[0004] Primary lithium electrochemical cells typically employ an
anode of lithium metal or lithium alloy, preferably a
lithium-aluminum alloy; a cathode containing an electrochemically
active material consisting of a transition metal oxide, preferably
manganese dioxide; and an electrolyte containing a chemically
stable lithium salt dissolved in an organic solvent or a mixture of
organic solvents. (The term "anode active material" or "cathode
active material" as used herein shall be understood to mean
material in the anode or cathode, respectively, which undergoes
useful electrochemical reaction during cell discharge, contributing
to the cell's capacity and voltage.)
[0005] The lithium anode is preferably formed from a sheet or foil
of lithium metal or lithium alloy without any substrate or lithium
metal deposited or coated on a metallic substrate such as copper or
other metals. A lithium primary cell referenced hereinafter as
having an anode comprising "lithium" shall be understood to mean an
anode of lithium metal or a lithium alloy. If a lithium-aluminum
alloy is employed, the aluminum is present in a very small amount,
typically less than about 1 wt % of the alloy. The addition of
aluminum primarily serves to improve the low temperature
performance of the lithium anode in lithium primary cells.
[0006] Manganese dioxides suitable for use in lithium primary cells
include both chemically produced manganese dioxide known as
"chemical manganese dioxide" or "CMD" and electrochemically
produced manganese dioxide known as "electrolytic manganese
dioxide" or "EMD". CMD can be produced economically and in high
purity, for example, by the methods described by Welsh et al. in
U.S. Pat. No. 2,956,860. However, CMD typically does not exhibit
energy or power densities in lithium cells comparable to those of
EMD. Typically, EMD is manufactured commercially by the direct
electrolysis of a bath containing manganese sulfate dissolved in a
sulfuric acid solution. Processes for the manufacture of EMD and
representative properties are described in "Batteries", edited by
Karl V. Kordesch, Marcel Dekker, Inc., New York, Vol. 1, 1974,
pp.433-488. Manganese dioxide produced by electrodeposition
typically is a high purity, high density, "gamma(.gamma.)-MnO.sub.2
" phase, which has a complex crystal structure containing irregular
intergrowths of a "ramsdellite"-type MnO.sub.2 phase and a smaller
portion of a beta(.beta.)- or "pyrolusite"-type MnO.sub.2 phase as
described by dewolfe (Acta Crystallographica, 12, 1959,
pp.341-345). The gamma(.gamma.)-MnO.sub.2 structure is discussed in
more detail by Burns and Burns (e.g., in "Structural Relationships
Between the Manganese (IV) Oxides", Manganese Dioxide Symposium, 1,
The Electrochemical Society, Cleveland, 1975, pp. 306-327).
[0007] Electrochemical manganese dioxide (EMD) is the preferred
manganese dioxide for use in primary lithium cells. However, before
it can be used, it must be heat-treated to remove residual water.
The term "residual water", as used herein includes surface-adsorbed
water, noncrystalline water (i.e., water physisorbed or occluded in
pores), as well as lattice water. Heat-treatment of EMD prior to
its use in lithium cells is well known and has been described by
Ikeda et al. (e.g., in "Manganese Dioxide as Cathodes for Lithium
Batteries", Manganese Dioxide Symposium, Vol. 1, The
Electrochemical Society, Cleveland, 1975, pp. 384-401).
[0008] EMD suitable for use in primary lithium cells can be
heat-treated at temperatures between about 200 and 350.degree. C.
as taught by Ikeda et al. in U.S. Pat. No. 4,133,856. This
reference also discloses that it is preferable to heat-treat the
EMD in two steps. The first step is performed at temperatures up to
about 250.degree. C. in order to drive off surface and
non-crystalline water. The EMD is heated in a second step to a
temperature between about 250 and 350.degree. C. to remove the
lattice water. This two-step heat-treatment process improves the
discharge performance of primary lithium cells, primarily because
surface, non-crystalline, and lattice water are all removed. An
undesirable consequence of this heat-treatment process is that EMD
having the .gamma.-MnO.sub.2-type structure, is gradually converted
to EMD having a gamma/beta (.gamma./.beta.)-MnO.sub.2-type
structure. The term "gamma/beta-MnO.sub.2" as used in the art
reflects the fact (as described by Ikeda et al.) that a significant
portion of the .gamma.-MnO.sub.2 (specifically, the
ramsdellite-type MnO.sub.2 phase) is converted to .beta.-MnO.sub.2
phase during heat-treatment. At least about 30 percent by weight
and typically between about 60 and 90 percent by weight of the
ramsdellite-type MnO.sub.2 phase is converted to .beta.-MnO.sub.2
during conventional heat treatment of .gamma.-MnO.sub.2 as taught,
for example, in U.S. Pat. No. 4,921,689. The resulting
.gamma./.beta.-MnO.sub.2 phase is less electrochemically active
than an EMD in which the .gamma.-MnO.sub.2 phase contains a higher
fraction of ramsdellite-type MnO.sub.2 relative to
.beta.-MnO.sub.2. Thackeray et al. have disclosed in U.S. Pat. No.
5,658,693 that cathodes containing such .beta.-MnO.sub.2-enriched
phases exhibit less capacity for lithium uptake during discharge in
lithium cells.
[0009] One consequence of the electrodeposition process used to
prepare EMD is that the formed EMD typically contains "residual
surface acidity" from the sulfuric acid of the electrolytic bath.
This "residual surface acidity" must be neutralized, for example,
with basic aqueous solution, before the EMD can be used in cathodes
for primary lithium cells. Suitable aqueous bases include: sodium
hydroxide, ammonium hydroxide (i.e., aqueous ammonia), calcium
hydroxide, magnesium hydroxide, potassium hydroxide, lithium
hydroxide, and combinations thereof. Typically, commercial EMD is
neutralized with a strong base such as sodium hydroxide because it
is highly effective and economical.
[0010] An undesirable consequence of the acid neutralization
process is that alkali metal cations can be introduced into
ion-exchangeable sites on the surface of the EMD particles. For
example, when sodium hydroxide is used for acid neutralization,
sodium cations can be trapped in the surface sites. This is
especially undesirable for EMD used in cathodes of primary lithium
cells because during cell discharge the sodium cations can be
released into the electrolyte, deposit onto the lithium anode, and
degrade the lithium passivating layer. Further, the deposited
sodium cations can be reduced to sodium metal, react with the
organic electrolyte solvents, and generate gas, thereby
substantially decreasing the storage life of the cells.
[0011] A process for converting commercial grade EMD that has been
neutralized with sodium hydroxide to the lithium neutralized form
is disclosed by Capparella et al. in U.S. Pat. No. 5,698,176 and
related Divisional U.S. Pat. No. 5,863,675. The disclosed process
includes the steps of: (a) mixing sodium hydroxide neutralized EMD
with an aqueous acid solution to exchange the sodium cations with
hydrogen ions and produce an intermediate with reduced sodium
content; (b) treating the intermediate with lithium hydroxide or
another basic lithium salt to exchange the hydrogen ions with
lithium cations; (c) heat-treating the lithium ion-exchanged EMD at
a temperature of at least about 350.degree. C. to remove residual
water.
[0012] A method for preparing a lithiated manganese dioxide and its
use in primary lithium cells as cathode active material in primary
lithium cells is described in U.S. Pat. No. 6,190,800 (Iltchev)
herein incorporated by reference. The lithiated manganese dioxide
recited in this reference is a heat treated lithiated manganese
dioxide product having the formula Li.sub.yMnO.sub.2-.delta.,
wherein 0.075.ltoreq.y.ltoreq.0.175 and
0.01.ltoreq..delta..ltoreq.0.06, and a predominantly
gamma(.gamma.)-MnO.sub.2-type crystal structure.
[0013] Thus, as evidenced by the cited prior art, the methods used
to prepare active cathode materials comprising manganese dioxide or
lithiated manganese dioxide suitable for cathodes in a primary
lithium cells require additional refinement in order to
substantially improve performance of the lithium cells
incorporating such active cathode materials.
SUMMARY OF THE INVENTION
[0014] A principal aspect of the invention is directed to a primary
(nonrechargeable) lithium cell having an anode comprising lithium,
a non-aqueous electrolyte, and a cathode comprising a copper
vanadate of formula CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 as
cathode active material. The CuV.sub.2O.sub.6 or
Cu.sub.2V.sub.2O.sub.7 can be used as cathode active material alone
or in any admixture thereof. The CuV.sub.2O.sub.6 can be used in
admixture with MnO.sub.2 in any mixture thereof to form the cathode
active material for the lithium cell. It shall be understood that a
portion of the MnO.sub.2 in this case can be in the form of a
manganese dioxide such as lithiated manganese dioxide or all of the
MnO.sub.2 can be in the form of a lithiated manganese dioxide. The
MnO.sub.2 is preferably heat treated to remove residual water. (The
term "a manganese dioxide" shall be understood to include MnO.sub.2
and lithiated manganese dioxide.) The lithiated manganese dioxide,
for example, as referenced above and hereinafter can have the
formula Li.sub.yMnO.sub.2-.delta., wherein
0.075.ltoreq.y.ltoreq.0.175 and 0.01.ltoreq..delta..ltoreq.0.06
recited in U.S. Pat. No. 6,190,800. Alternatively, the
Cu.sub.2V.sub.2O.sub.7 if employed as cathode active material can
be used in admixture with MnO.sub.2 in any mixture thereof to form
the cathode active material for the lithium cell. In such case it
shall be understood that a portion of the MnO.sub.2 or all of the
MnO.sub.2 present in the cathode can be in the form of a lithiated
manganese dioxide, for example, a lithiated manganese dioxide
having the formula Li.sub.yMnO.sub.2-.delta., wherein
0.075.ltoreq.y.ltoreq.0.175 and 0.01.ltoreq..delta..ltoreq.0.06 as
recited in U.S. Pat. No. 6,190,800.
[0015] Also, the cathode active material for the lithium cell can
comprise mixtures of CuV.sub.2O.sub.6, Cu.sub.2V.sub.2O.sub.7, and
MnO.sub.2. All or a portion of the MnO.sub.2 in such mixtures can
be in the form of a lithiated manganese dioxide. It will be
appreciated that the MnO.sub.2 is desirably heat treated to remove
residual water thereby making it more suitable for use as cathode
active material in the lithium cell. A conductive carbon,
preferably graphite such as natural, or synthetic graphite,
preferably expanded graphite, is added to the cathode mixture to
improve conductivity.
[0016] It has been determined that the primary lithium cell of the
invention can comprise a conventional anode, namely, a sheet of
lithium or lithium alloy, e.g. lithium-aluminum alloy, preferably,
comprising at least 99 percent by weight lithium. (An anode
comprising "lithium" as referenced herein shall be understood to
mean an anode of lithium metal or such lithium alloy.) The cell may
be in the form of a button cell or a spirally wound cell. The
electrolyte can be non-aqueous electrolyte, conventionally used in
primary lithium cells having a lithium anode and MnO.sub.2 cathode.
For example, by way of non-limiting example, the electrolyte can be
a lithium salt, such as lithium perchlorate (LiClO.sub.4) or
lithium trifluoromethylsulfonate (LiCF.sub.3SO.sub.3) dissolved in
an organic solvent, for example, dimethoxyethane (DME) or, ethylene
carbonate (EC) and propylene carbonate (PC). Gel type polymer
electrolytes used in conventional lithium-ion rechargeable cells
could also be suitable. The separator can be selected from
conventional separators for primary lithium cells, for example, the
separator can be of microporous polypropylene.
[0017] The copper in CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7
compound has a +2 valence and the vanadium a +5 valence. The
Cu.sup.+2 and V.sup.+5 are available for reduction to copper metal
and vanadium (V.sup.+3) during discharge. On such basis the
CuV.sub.2O.sub.6 has a high theoretical specific capacity, namely,
615 milliAmp-hour/g and the Cu.sub.2V.sub.2O.sub.7 has a high
theoretical capacity of 629 milliAmp-hour/g. This is much higher
than the theoretical specific capacity of MnO.sub.2, which is 308
milliAmp-hour/g. Thus, when CuV.sub.2O.sub.6 or
Cu.sub.2V.sub.2O.sub.7 compounds are used as cathode active
material in a primary lithium cell, this results in higher capacity
and also higher total "energy output" when compared to same cell
having a MnO.sub.2 cathode.
[0018] When CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 are each
used alone without any added MnO2, the CuV.sub.2O.sub.6 or
Cu.sub.2V.sub.2O.sub.7 desirably comprises between about 60 and 95
percent by weight of the total cathode (electrolyte free basis) .
When CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7 are used in
admixture without any added MnO2, the mixture of CuV.sub.2O.sub.6
and Cu.sub.2V.sub.2O.sub.7 desirably comprises between about 60 and
95 percent by weight of the total cathode (electrolyte free basis),
typically between about 60 and 93 percent by weight of the total
cathode (electrolyte free basis).
[0019] In cathode mixtures of CuV.sub.2O.sub.6 and MnO2 or mixtures
of Cu.sub.2V.sub.2O.sub.7 and MnO2, the CuV.sub.2O.sub.6 or
Cu.sub.2V.sub.2O.sub.7 in such mixtures desirably comprises between
about 1 and 95 percent by weight of the total cathode (electrolyte
free basis), desirably between about 60 and 95 percent by weight of
the total cathode (electrolyte free basis). Typically, the
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 in such mixtures
comprises between about 60 and 93 percent by weight of the total
cathode (electrolyte free basis). In such mixture the MnO.sub.2 may
typically comprise between about 10 and 75 percent by weight of the
total cathode (electrolyte free basis).
[0020] If the cathode comprises both CuV.sub.2O.sub.6 and
Cu.sub.2V.sub.2O.sub.7 in admixture with manganese dioxide, then
the total amount of CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7
together is desirably between about 1 and 95 percent by weight of
the total cathode (electrolyte free basis), desirably between about
60 and 95 percent by weight of the total cathode (electrolyte free
basis). Typically, the amount of CuV.sub.2O.sub.6 and
Cu.sub.2V.sub.2O.sub.7 together in such mixtures comprises between
about 60 and 93 percent by weight of the total cathode (electrolyte
free basis).
BRIEF DESCRIPTION OF THE DRAWING
[0021] The FIGURE is a cross sectional view of a typical primary
lithium electrochemical button cell.
DETAILED DESCRIPTION
[0022] A primary lithium electrochemical cell can be fabricated in
the form of a button or coin cell 10 as shown in the FIGURE. The
primary lithium cell can also be fabricated in the form of a wound
cell, for example, as shown in U.S. Pat. No. 4,707,421, herein
incorporated by reference. In the button cell shown in the figure,
a disk-shaped cylindrical housing 30 is formed having an open end
32 and a closed end 38. Housing 30 is preferably formed from
nickel-plated steel, for example. An electrical insulating member
40, preferably a cylindrical member having a hollow core, is
inserted into housing 30 so that the outside surface of insulating
member 40 abuts and lines the inside surface of housing 30.
Alternatively, the inside surface of housing 30 may be coated with
a polymeric material that solidifies into insulator 40 abutting the
inside surface of housing 30. Insulator 40 can be formed from a
variety of thermally stable insulating materials, for example,
nylon or polypropylene. A cathode current collector 15 comprising a
metallic grid can be inserted into the cell so that it abuts the
inside surface of the closed end 38 of the housing 30. The cathode
current collector 15 can be welded onto the inside bottom of the
closed end 38 of the housing 30. An optional conductive carbon
layer 72 comprising a mixture of graphite and
polytetrafluoroethylene (PTFE) binder can be compressed into the
cathode current collector 15 and the cathode material 70 coated
onto such conductive layer 72. This may be termed a "staged"
cathode construction.
[0023] A layer of cathode material 70 of the invention comprising
CuV2O6 or Cu2V2O7 or any mixture thereof as active cathode
material, may thus be inserted over optional conductive layer 72
overlying cathode current collector 15. The cathode active material
in cathode 70 can be composed entirely of CuV2O6. Alternatively,
cathode material 70 can comprise mixtures of CuV2O6 and manganese
dioxide or mixtures of CuV2O6 and lithiated manganese dioxide as
well as mixtures of CuV2O6, manganese dioxide and lithiated
manganese dioxide as the cathode active material therein. The
lithiated manganese dioxide, for example, can have the form as
above referenced in U.S. Pat. No. 6,190,800, herein incorporated by
reference.
[0024] Alternatively, the cathode active material in cathode 70 can
be composed entirely of Cu.sub.2V.sub.2O.sub.7 or mixtures of
CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7 with or without an
MnO.sub.2 or lithiated MnO.sub.2 added.
[0025] In the absence of the conductive layer 72, the layer of
cathode material 70 is compressed into cathode current collector
15. A separator sheet 60 is placed overlying cathode layer 70.
Nonaqueous electrolyte is added so that it fully penetrates through
separator sheet 60 and cathode layer 70. A layer of anode material
50, typically lithium or lithium alloy is placed over separator
sheet 60. The anode cover 20, formed preferably from nickel-plated
steel, is inserted into open end 32 of housing 30 and peripheral
edge 35 of housing 30 is crimped over the exposed insulator edge 42
of insulating member 40. The peripheral edge 35 bites into
insulator edge 42 closing housing 30 and tightly sealing the cell
contents therein. The anode cover 20 also functions as the negative
terminal of the cell and housing 30 at the closed end 38 functions
as the positive terminal of the cell.
[0026] Alternatively, a primary lithium cylindrical cell can be
fabricated comprising a spirally wound anode and cathode with a
separator sheet positioned therebetween. This electrode
configuration for primary lithium cells is well known in the art
and an embodiment thereof is described in detail, for example, in
U.S. Pat. No. 4,707,421. Compositions for the electrodes,
separator, and electrolyte as disclosed in U.S. Pat. No. 4,707,421,
herein incorporated by reference, can be used for the primary
lithium cells of the present invention except that the cathode
comprises CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 or mixtures
thereof which can include a manganese dioxide added thereto as
above referenced.
Synthesis of CuV2O6 and Cu2V2O7
[0027] Copper vanadate (CuV.sub.2O.sub.6) was prepared by dry
mixing copper oxide (CuO) powder with vanadium pentoxide
(V.sub.2O.sub.5) powder in one to one molar ratio. The copper oxide
and copper vanadate powders, available from Alfa Aesar Co., each
had an average particle size of between about 200 and 300 micron.
Vanadium pentoxide was handled with care within a protective
environment to prevent direct inhalation. The powder mixture was
ball milled in 1 kilogram batches in an electric mixer using
zirconia balls as inert milling medium. The powder was mixed in
this manner for up to 24 hours to achieve a homogeneous mixture,
which was then passed through a sieve to remove the zirconia balls.
The filtered mixture was then placed in a ceramic container and
heated in a conventional oven at a temperature of about 620.degree.
C. for about 48 hours in ambient atmosphere. The vanadium pentoxide
(V.sub.2O.sub.5) and copper oxide (CuO) powders reacted to form a
blue/black powder of single phase crystalline particles having the
formula CuV.sub.2O.sub.6.
[0028] The copper vanadate (CuV.sub.2O.sub.6) product synthesized
in the above manner had the following properties: The
CuV.sub.2O.sub.6 product had a particle size distribution wherein
10% by volume of the product fell below 19.4 micron; 50% by volume
fell below 36.6 micron, and 100% by volume fell below 215 micron.
The value mean diameter (VMD) which approximates the true mean
diameter of the CuV.sub.2O.sub.6 particles was 43.6 micron. The
CuV.sub.2O.sub.6 had a BET surface area of about 0.18 m.sup.2/g.
The term BET surface area (m.sup.2/g) as used herein shall mean the
standard measurement of particulate surface area by gas (nitrogen
and/or other gasses) porosimetry as is recognized in the art. The
BET surface area measures the total surface area on the exterior of
the particle and also that portion of the surface area defined by
the open pores within the particle available for gas adsorption and
desorption when applied. BET surface area determinations (Brunauer,
Emmett and Taylor, method) as reported herein is carried out in
accordance with ASTM Standard Test Method D4820-99.
[0029] The CuV.sub.2O.sub.6 product had a low solubility of less
than 5 parts per million (PPM) in water at room temperature. The
CuV.sub.2O.sub.6 product had a measured real density of 4.37
g/cm.sup.3 and a calculated theoretical density of 4.396 g/cm3. The
real density of a solid is the solid sample weight divided by real
volume. The theoretical capacity of the CuV.sub.2O.sub.6 based on
reduction of 6 electrons per molecule (Cu.sup.+2 to Cu and V.sup.+5
to V.sup.+3) is calculated as 615 InAh/g.
[0030] The out of cell gassing was determined for cathodes
comprising CuV.sub.2O.sub.6 in admixture with lithium
trifluoromethane sulfonate (CF.sub.3SO.sub.3Li) electrolyte. The
cathode mixture for the gassing test contained 4.5 g
CuV.sub.2O.sub.6 and 5 ml electrolyte. The electrolyte comprised a
0.6 M solution of the (CF.sub.3SO.sub.3Li) in an organic solvent
mixture of ethylene carbonate (EC), propylene carbonate (PC), and
dimethoxyethane (DME). A comparative cathode mixture comprising
manganese dioxide and same electrolyte was prepared and also tested
for out of cell gassing. Each mixture was kept in closed chamber at
70.degree. C. for five days and the amount of gassing was
determined by measuring the internal gas pressure within the
chamber. The chamber housing the test cathode comprising
CuV.sub.2O.sub.6 and same electrolyte exhibited an increase in
internal pressure of about 20 psig. By contrast the chamber housing
the comparative cathode mixture of MnO.sub.2 and electrolyte
exhibited an increase in internal gas pressure to 45 psig.
[0031] Copper vanadate (Cu.sub.2V.sub.2O.sub.7) was synthesized in
a similar manner using copper oxide (CuO) and vanadium pentoxide
(V.sub.2O.sub.5) as starting materials. However, the reaction
mixture was prepared by mixing the CuO and V.sub.2O.sub.5 powders
in a stoichiometric ratio of 2 moles CuO to one mole
V.sub.2O.sub.5. The CuO and V.sub.2O.sub.5 powders each had average
particle size of between about 200 and 300 micron as described
above. The mixture was blended with an inert media of zirconia
balls in an electric mixer for up to 24 hours until a homogenous
mixture was achieved. The powder mixture was separated from the
inert media and then placed into a ceramic container. The powder
mixture in ceramic container was heated in an oven at a final
temperature of about 700.degree. C. for about 48 hours in ambient
atmosphere. At this temperature the CuO and V.sub.2O.sub.5 powders
reacted to form a crystalline product having of formula
Cu.sub.2V.sub.2O.sub.7.
[0032] The cathode 70 for the primary lithium cell of the invention
consists of a cathode active material mixed with suitable polymeric
binders, for example, polytetrafluoroethylene, and conductive
agents, for example, carbon black and graphite, to produce a
cathode paste or slurry. The cathode paste can be applied to
current collector 15 comprising a highly porous sintered, felted,
or foamed electrically-conductive substrate, for example, a
stainless steel grid, an expanded metal foam or a metal foil. The
cathode active material in cathode 70 can comprise the
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 alone or in any mixtures
thereof. Manganese dioxide or lithiated manganese dioxide can be
added in any percent by weight as additional cathode active
material in admixture with the CuV2O6 or Cu2V2O7 cathode active
material. (The manganese dioxide, if included as additional cathode
active material is desirably conventional heat-treated manganese
dioxide.) Cathode pieces of the appropriate size can be cut from
the coated substrate.
[0033] The anode 50 comprises anode active material preferably of
lithium or a lithium alloy. The anode 50 can be a solid sheet of
lithium. The anode 50 is desirably formed of a continuous sheet of
lithium metal (99.8 wt. % pure). Alternatively, anode 50 can be an
alloy of lithium and an alloy metal, for example, an alloy of
lithium and aluminum. An alloying metal, such as aluminum, can be
present at a low concentration, typically less than 1 wt. %. Upon
cell discharge the lithium in the alloy functions essentially as
pure lithium. Thus, the term "lithium or lithium metal" as used
herein and in the claims is intended to include such lithium alloy.
The lithium sheet, forming anode 50 does not require a substrate.
The lithium anode 50 is advantageously formed from an extruded
sheet of lithium metal having a thickness of desirably between
about 0.15 and 0.20 mm Alternatively, a much thicker lithium metal
anode of about 0.75 mm thick could be used for test coin cells, for
example, of the type referenced in the examples.
[0034] A separator layer 60 is located between the two electrodes.
The separator layer typically consists of a porous polymer film or
thin sheet that serves as a spacer and prevents electrical contact
between the cathode and anode while allowing electrolyte to move
freely through the pores. Suitable separators can include
relatively non-reactive polymers such as, for example, microporous
polypropylene, polyethylene, a polyamide (i.e., a nylon), a
polysulfone, or polyvinyl chloride (PVC). The separator has a
preferred thickness between about 10 microns and 200 microns and a
more preferred thickness between about 20 microns and 50
microns.
[0035] The anode 50, cathode 70 and separator 60 therebetween are
contained within housing 30. As described hereinabove, the cell can
take the form of a coin cell, button cell, cylindrical cell,
prismatic cell, laminar cell or other standard cell geometry. The
housing 30 is closed to provide a gas-tight and fluid-tight seal.
The housing 30 can be made of a metal such as nickel, nickel clad
or plated steel, stainless steel, aluminum or a plastic material
such as PVC, polypropylene, a polysulfone, an acrylic
acid-butadiene-styrene terpolymer (ABS), or a polyamide. The
housing 30 containing the electrodes and separator can be filled
with a suitable liquid or a polymeric nonaqueous electrolyte.
[0036] The nonaqueous electrolyte can be any nonaqueous electrolyte
or combination of nonaqueus electrolytes known in the art.
Typically, nonaqueous electrolytes suitable for use in a primary
lithium/MnO.sub.2 cell comprise a lithium salt dissolved in an
organic solvent or combination of organic solvents. Typically, the
salt is lithium perchlorate (LiClO.sub.4) or lithium
trifluoromethylsulfonate (LiCF.sub.3SO.sub.3) . Other suitable
electrolyte salts include: LiPF.sub.6, LiAsF.sub.6, LiBF.sub.4,
lithium bis(trifluoromethylsulfonyl) imide
(Li(CF.sub.3SO.sub.2).sub.2N), and lithium bis
(perfluoroethylsulfonyl) imide
(Li(CF.sub.3CF.sub.2SO.sub.2).sub.2N). Suitable organic solvents
include ethylene carbonate(EC), propylene carbonate(PC), butylene
carbonate, and the like; dimethylcarbonate (DMC); diethyl carbonate
(DEC), ethyl methyl carbonate (EMC), dimethoxyethane (DME);
dioxolane; gamma(.gamma.)-butyrolactone; diglyme; and mixtures
thereof. A preferred electrolyte composition consists of a 0.6 M
solution of lithium trifluoromethylsulfonate (CF.sub.3SO.sub.3Li;
available under the tradename, FC-122, from 3M) in a mixture of dry
ethylene carbonate, propylene carbonate, and dimethoxyethane. Once
filled with the nonaqueous electrolyte, the housing 30 is sealed to
confine the nonaqueous electrolyte and to inhibit the infiltration
of moisture and air into the cell.
[0037] The following examples illustrate the invention. Test cells
were prepared and balanced so that they were cathode limited,
(theoretical capacity of lithium divided by theoretical capacity of
total cathode actives above about 1). The cathode theoretical
capacity is calculated using the following theoretical specific
capacities: Li, 3860 mAh/g; MnO.sub.2, 308 mAh/g; CuV.sub.2O.sub.6,
615 mAh/g; and Cu.sub.2V.sub.2O.sub.7, 629 mAh/g.
EXAMPLE 1
Comparative--Lithium Anode/MnO2 Cathode
[0038] A button cell 10 is made in accordance with the above
description. The button cell 10 was a standard 2430 size having the
overall dimensions 24.47 mm diameter and 2.46 mm thickness. The
anode material 50 was as above described comprising a sheet of
lithium (99.8 wt. % pure). The anode 50 had a weight of .about.115
mg. In the test cells slight excess Li weight was used in
determining the specific capacity of cathode active material and
also to fill up the void volume inside the cells. The separator 60
was of microporous polypropylene membrane of basis weight between
about 13.5 and 16.5 g/m.sup.2 and about 0.025 mm thick.
[0039] Cathode 70 which was coated onto conductive carbon layer 72
had the following formulation: manganese dioxide (electrolytic
manganese dioxide, EMD), 70.0 wt. %, tetrafluoroethylene (Teflon
polymer), 3.0 wt. %, conducting carbon additive 27 wt. % (mixtures
of Shawinigan carbon black and particulate graphite such as
expanded graphite from Timcal Group in different ratios). The
manganese dioxide was heat treated in conventional manner to remove
residual water (non-crystalline water) therefrom before the cathode
coating 70 was prepared. The cathode 70 can be prepared by mixing
the above components in a conventional electric blender at room
temperature until a homogenous mixture is obtained. The cathode
mixture 70 can be coated on one side of the cathode current
collector 15. The cathode current collector was a stainless steel
expanded metal foil (EXMET stainless steel foil) having a basis
weight of about 0.024 g/cm.sup.3. After the anode 50 and cathode 70
is inserted with separator 60 the housing 30 is filled with the
above described electrolyte consisting of a 0.6 M solution of
lithium trifluoromethylsulfonate (CF.sub.3SO.sub.3Li; available
under the tradename, FC-122, from 3M) in a mixture of dry ethylene
carbonate, propylene carbonate, and dimethoxyethane. Cell 10 was
then sealed as above described.
1 Cathode Composition, wt. % MnO.sub.2 70.0 Tetrafluoroethylene 3.0
Teflon polymer Particulate graphite 27.0 Total 100.0
[0040] Fresh cells 10 were discharged at a constant current of 1
milliAmp and 10 milliAmp to a cut off of 1.5 volts. The 1 mA and 10
mA rate in the button cell corresponds to a rate of about 248 mA/g
and 171 mA/g, respectively, of the manganese dioxide cathode active
material. The cells specific capacity for actives (mAmp-hours/g)
and energy output for total cathode actives (mWatt-hours/g),
(mWatt-hours/cc) is reported in Table 1 for discharge at 1 milliamp
and Table 2 for discharge at 10 milliamp.
EXAMPLE 2
Lithium Anode/CuV2O6 Cathode
[0041] A button cell 10 is made as in Example 1 employing the same
size cell, same anode, same electrolyte and components, except that
the cathode compositon was changed to employ CuV.sub.2O.sub.6 as
cathode active material.
[0042] Cathode 70 has the following formulation: CuV.sub.2O.sub.6,
70 wt. %; particulate graphite (expanded graphite from Timcal
Group), 27 wt. %; tetrafluoroethylene (Teflon) binder, 3 wt. %. The
cathode 70 can be prepared by mixing the above components in a
conventional electric blender at room temperature until a
homogenous mixture is obtained. The cathode mixture 70 can be
coated on one side of the cathode current collector 15. The cathode
current collector was a stainless steel expanded metal foil (EXMET
stainless steel foil) having a basis weight of about 0.024
g/cm.sup.3. The cathode composition is summarized as follows:
2 Cathode Composition, wt. % CuV.sub.2O.sub.6 70.0
Tetrafluoroethylene 3.0 Teflon polymer Particulate graphite 27.0
Total 100.0
[0043] Fresh lithium button cells 10 were prepared having a cathode
containing 0.04 gram copper vanadate (CuV.sub.2O.sub.6) and were
balanced so that they were cathode limited. The cells were
discharged at a constant current of 1 milliAmp and 10 milliAmp to a
cut off of 1.5 volts. The 1 mA and 10 mA rate in the button cell
corresponds to a rate of about 25 mA/g and 250 mA/g, respectively,
of the cathode active material. (Also 1 milliAmp rate in the above
button cell using 0.04 gram CuV.sub.2O.sub.6 corresponds to
approximately a .about.150 milliAmp rate for a 2/3 A cell using
about 6 gram of CuV2O6. The 10 milliAmp rate in the above button
cell using 0.04 gram CuV.sub.2O.sub.6 corresponds to approximately
a .about.1500 milliAmp rate for a 2/3 A cell using about 6 gm of
CuV.sub.2O.sub.6 actives). The cells specific capacity for actives
(mAmp-hours/g) and energy output for total cathode actives
(mwatt-hours/g), (mWatt-hours/cc) is reported in Table 1 for
discharge at 1 milliamp and Table 2 for discharge at 10
milliamp.
EXAMPLE 3
Lithium Anode/Cu2V2O7 Cathode
[0044] A button cell 10 is made as in Example 1 employing the same
size cell, same anode, same electrolyte and components, except that
the cathode composition was changed to employ
Cu.sub.2V.sub.2O.sub.7 as cathode active material.
[0045] Cathode 70 has the following formulation:
Cu.sub.2V.sub.2O.sub.7, 70 wt. %; particulate graphite (expanded
graphite from Timcal Group), 27 wt. %; tetrafluoroethylene (Teflon)
binder, 3 wt. %. The cathode 70 can be prepared by mixing the above
components in a conventional electric blender at room temperature
until a homogenous mixture is obtained. The cathode mixture 70 can
be coated on one side of the cathode current collector 15. The
cathode current collector was a stainless steel expanded metal foil
(EXMET stainless steel foil) having a basis weight of about 0.024
g/cm.sup.3. The cathode composition is summarized as follows:
3 Cathode Composition, wt. % Cu.sub.2V.sub.2O.sub.7 70.0
Tetrafluoroethylene 3.0 Teflon polymer Particulate graphite 27.0
Total 100.0
[0046] Fresh lithium button cells 10 were prepared having a cathode
containing 0.04 gram copper vanadate (Cu.sub.2V.sub.2O.sub.7) and
were balanced so that they were cathode limited. The cells were
discharged at a constant current of 1 milliAmp and 10 milliAmp to a
cut off of 1.5 volts. The 1 mA and 10 mA rate in the button cell
corresponds to a rate of about 25 mA/g and 250 mA/g, respectively,
of the cathode active material. (Also 1 milliAmp rate in the above
button cell using 0.04 gram Cu.sub.2V.sub.2O7 corresponds to
approximately a .about.150 milliAmp rate for a 2/3 A cell using
about 6 gram of CuV2O6. The 10 milliAmp rate in the above button
cell using 0.04 gram CuV.sub.2O.sub.6 corresponds to approximately
a .about.1500 milliAmp rate for a 2/3 A cell using about 6 gm of
Cu.sub.2V.sub.2O.sub.6 actives). The cells specific capacity for
actives (mAmp-hours/g) and energy output for total cathode actives
(mwatt-hours/g), (mWatt-hours/cc) is reported in Table 1 for
discharge at 1 milliamp and Table 2 for discharge at 10
milliamp.
EXAMPLE 4
Lithium Anode/(CuV2O6+MnO.sub.2 Cathode
[0047] A button cell 10 is made as in Example 1 employing the same
size cell, same anode, same electrolyte and components, except that
the cathode composition was changed to employ CuV.sub.2O.sub.6 in
admixture with MnO.sub.2 as cathode active material.
[0048] Cathode 70 has the following formulation: CuV.sub.2O.sub.6,
35 wt. % MnO.sub.2, 35 wt. %; particulate graphite (expanded
graphite from Timcal Group), 27 wt. %; tetrafluoroethylene (Teflon)
binder, 3 wt. %. The MnO.sub.2 was heat treated to remove residual
water before use in the cathode. The cathode 70 can be prepared by
mixing the above components in a conventional electric blender at
room temperature until a homogenous mixture is obtained. The
cathode mixture 70 can be coated on one side of the cathode current
collector 15. The cathode current collector was a stainless steel
expanded metal foil (EXMET stainless steel foil) having a basis
weight of about 0.024 g/cm.sup.3. The cathode composition is
summarized as follows:
4 Cathode Composition, wt. % CuV.sub.2O.sub.6 35.0 MnO2 35.0
Tetrafluoroethylene 3.0 Teflon polymer Particulate graphite 27.0
Total 100.0
[0049] Fresh lithium button cells 10 were prepared having a cathode
containing 0.1 gram cathode actives (CuV.sub.2O.sub.6+MnO2) and
were balanced so that they were cathode limited. The cells were
discharged at a constant current of 1 milliAmp and 10 milliAmp to a
cut off of 1.5 volts. The 1 mA and 10 mA rate in the button cell
corresponds to a rate of about 10 mA/g and 100 mA/g, respectively,
of the cathode active material. (Also 1 milliAmp rate in the above
button cell using 0.1 gram cathode actives (CuV.sub.2O.sub.6 plus
MnO.sub.2) corresponds to approximately a .about.60 milliAmp rate
for a 2/3 A cell using about 6 gram of same composition cathode
actives. The 10 milliAmp rate in the above button cell using 0.1
gram cathode actives (CuV.sub.2O.sub.6 plus MnO.sub.2) corresponds
to approximately a .about.600 milliAmp rate for a 2/3 A cell using
about 6 gm of same composition cathode actives). The cells specific
capacity for actives (mAmp-hours/g) and energy output for total
cathode actives (mWatt-hours/g), (mWatt-hours/cc) is reported in
Table 1 for discharge at 1 milliamp and Table 2 for discharge at 10
milliamp.
EXAMPLE 5
Lithium Anode/CuV2O6+Cu2V2O7 Cathode
[0050] A button cell 10 is made as in Example 1 employing the same
size cell, same anode, same electrolyte and components, except that
the cathode composition was changed to employ CuV.sub.2O.sub.6 in
admixture with Cu.sub.2V.sub.2O.sub.7 as cathode active
material.
[0051] Cathode 70 has the following formulation: CuV.sub.2O.sub.6,
52.5 wt. %; Cu.sub.2V.sub.2O.sub.7, 17.5 wt. %; particulate
graphite (expanded graphite from Timcal Group), 27 wt. %;
tetrafluoroethylene (Teflon) binder, 3 wt. %. The MnO.sub.2 was
heat treated to remove residual water before use in the cathode.
The cathode 70 can be prepared by mixing the above components in a
conventional electric blender at room temperature until a
homogenous mixture is obtained. The cathode mixture 70 can be
coated on one side of the cathode current collector 15. The cathode
current collector was a stainless steel expanded metal foil (EXMET
stainless steel foil) having a basis weight of about 0.024
g/cm.sup.3. The cathode composition is summarized as follows:
5 Cathode Composition, wt. % CuV.sub.2O.sub.6 52.5
Cu.sub.2V.sub.2O.sub.7 17.5 Tetrafluoroethylene 3.0 Teflon polymer
Particulate graphite 27.0 Total 100.0
[0052] resh lithium button cells 10 were prepared having a cathode
containing 0.1 gram copper vanadates (CuV.sub.2O.sub.6 plus
Cu.sub.2V.sub.2O.sub.7) and were balanced so that they were cathode
limited. The cells were discharged at a constant current of 1
milliAmp and 10 milliAmp to a cut off of 1.5 volts. The 1 mA and 10
mA rate in the button cell corresponds to a rate of about 10 mA/g
and 100 mA/g, respectively, of the cathode active material. (Also 1
milliAmp rate in the above button cell using 0.1 gram cathode
actives (CuV.sub.2O.sub.6 plus Cu.sub.2V.sub.2O.sub.7) corresponds
to approximately a .about.60 milliAmp rate for a 2/3 A cell using
about 6 gram of same composition of cathode actives. The 10
milliAmp rate in the above button cell using 0.1 gram cathode
actives (CuV.sub.2O.sub.6 plus Cu.sub.2V.sub.2O.sub.7) corresponds
approximately a .about.600 milliAmp rate for a 2/3 A cell using
about 6 gm of same composition of cathode actives). The cells
specific capacity for actives (mAmp-hours/g) and energy output for
total cathode actives (mWatt-hours/g), (mWatt-hours/cc) is reported
in Table 1 for discharge at 1 milliamp and Table 2 for discharge at
10 milliamp.
6TABLE 1 Fresh Lithium Button Cell With Cathode.sup.1 Comprising
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 (and mixtures)
Discharged at 1 mAmp. to 1.5 Volt cut-off at Ambient Temperature
Specific Energy Energy Capacity Out out Cathode for Total of Total
of Total Actives Cathode Cathode Cathode Weight % of Actives
Actives Actives, Example.sup.2 total cathode) (mAh/g) (mWh/g)
(mWh/cc) Ex. 1 MnO.sub.2 (70 wt. %) 248 611 2345 Comparison Ex. 2
CuV.sub.2O.sub.6 (70 wt. %) 424 1031 4435 Ex. 3
Cu.sub.2V.sub.2O.sub.7 (70 wt. %) 388 893 3618 Ex. 4
CuV.sub.2O.sub.6 (35 wt. %); 327 695 3161 MnO.sub.2 (35 wt. %) Ex.
5 CuV.sub.2O.sub.6 (52.5 wt. %); 356 713 3021
Cu.sub.2V.sub.2O.sub.7(17.5 wt. %) Notes: .sup.1The
CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7 in the above table was
synthesized at about 620.degree. C. and 700.degree. C.,
respectively, resulting in a single phase product with desirable
microstructure and generally high # particle size distribution. The
cathodes comprising CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 and
mixtures thereof exhibited very little gassing when the cells were
discharged. .sup.2Examples 1, 2 and 3 were based on cells with 0.04
gram of cathode actives. Examples 4 and 5 were based on cells with
0.1 gram cathode actives.
[0053]
7TABLE 2 Fresh Lithium Button Cell With Cathode.sup.1 Comprising
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 (and mixtures)
Discharged at 10 mAmp. to 1.5 Volt cut-off at Ambient Temperature
Specific Energy Energy Capacity Out out Cathode for Total of Total
of Total Actives Cathode Cathode Cathode Weight % of Actives
Actives Actives, Example.sup.2 total cathode) (mAh/g) (mWh/g)
(mWh/cc) Ex. 1 MnO.sub.2 (70 wt. %) 171 380 1823 Comparison Ex. 2
CuV.sub.2O.sub.6 (70 wt. %) 385 870 3742 Ex. 3
Cu.sub.2V.sub.2O.sub.7 (70 wt. %) 358 729 2952 Ex. 4
CuV.sub.2O.sub.6 (35 wt. %); 248 545 2485 MnO.sub.2 (35 wt. %) Ex.
5 CuV.sub.2O.sub.6 (52.5 wt. %); 385 859 3652
Cu.sub.2V.sub.2O.sub.7(17.5 wt. %) Notes: .sup.1The
CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7 in the above table was
synthesized at about 620.degree. C. and 700.degree. C.,
respectively, resulting in a single phase product with desirable
microstructure and generally high # particle size distribution. The
cathodes comprising CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 and
mixtures thereof exhibited very little gassing when the cells were
discharged. .sup.2Examples 1, 2 and 3 were based on cells with 0.04
gram of cathode actives. Examples 4 and 5 were based on cells with
0.1 gram cathode actives.
[0054] The test lithium cells employing cathodes comprising
CuV.sub.2O.sub.6 or Cu.sub.2V.sub.2O.sub.7 or mixtures thereof show
generally much higher actual specific capacity (mAmp-hrs/g of total
cathode actives) and higher energy output (mwatt-hr per gram or
mwatt-hr per cubic centimeter of total cathode actives) than the
comparative lithium cells with only MnO.sub.2 actives. This was
generally true at both discharge rates employed 1 mAmp (Table 1) or
10 mAmp rate (Table 2) and thus reflects the attractiveness of the
CuV.sub.2O.sub.6 and Cu.sub.2V.sub.2O.sub.7 vanadates as cathode
active material for primary lithium cells.
[0055] Although the present invention has been described with
reference to specific embodiments, it will be appreciated that
variations within the concept of the invention are possible. Thus,
the invention is not intended to be limited to the specific
embodiments, but rather is defined by the claims and equivalents
thereof.
* * * * *